August 30, 2006

Earth’s formerly thin ozone layer is recovering

WASHINGTON (Reuters) - Earth's protective ozone layer,
which was notably thinning in 1980, may be fully recovered by
mid-century, climate scientists said on Wednesday.

Ozone in the stratosphere, outside the polar regions,
stopped thinning in 1997, the scientists found after analyzing
25 years worth of observations.

The ozone layer shields the planet from the sun's harmful
ultraviolet radiation, but human-made chemicals -- notably the
chlorofluorocarbons found in some refrigerants and aerosol
propellants -- depleted this stratospheric ozone, causing the
protective layer to get thinner.

The scientists said the ozone layer's comeback is due in
large part to compliance with an 1987 international agreement
called the Montreal Protocol, which aimed to limit emissions of
ozone-depleting chemicals.

"These results confirm the Montreal Protocol and its
amendments have succeeded in stopping the loss of ozone in the
stratosphere," said Eun-Su Yang of the Georgia Institute of
Technology, who led a team that analyzed the data.

"At the current recovery rate ... the global ozone layer
could be restored to 1980 levels -- the time that scientists
first noticed the harmful effects human activities were having
on atmospheric ozone -- sometime in the middle of this
century," Yang said in a statement.

While ozone is a beneficial shield in the stratosphere,
some six to 31 miles above Earth's surface, the ozone
encountered at ground level can be damaging to lung tissue and
plants and is a major component of smog.

The analysis was published in the Journal of Geophysical
Research - Atmospheres.

Researchers from NASA and other agencies reported in June
that the so-called ozone hole over Antarctica would recover by
around 2068, which is some 20 years later than previously

The Antarctic ozone hole is a massive loss of ozone that
occurs each spring in the Southern Hemisphere.

A similar, though smaller and less severe, ozone hole has
been reported in the Arctic.